Network Working Group Y. Lee, Ed.
Internet Draft Huawei Technologies
Intended status: Standard Track R. Casellas, Ed.
Expires: August 6, 2019 CTTC
February 7, 2019
PCEP Extension for WSON Routing and Wavelength Assignment
draft-ietf-pce-wson-rwa-ext-13
Abstract
This document provides the Path Computation Element communication
Protocol (PCEP) extensions for the support of Routing and Wavelength
Assignment (RWA) in Wavelength Switched Optical Networks (WSON).
Path provisioning in WSONs requires a routing and wavelength
assignment (RWA) process. From a path computation perspective,
wavelength assignment is the process of determining which wavelength
can be used on each hop of a path and forms an additional routing
constraint to optical path computation.
Status of this Memo
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Table of Contents
1. Terminology....................................................3
2. Requirements Language..........................................3
3. Introduction...................................................3
4. Encoding of a RWA Path Request.................................6
4.1. Wavelength Assignment (WA) Object.........................6
4.2. Wavelength Selection TLV..................................8
4.3. Wavelength Restriction Constraint TLV.....................9
4.3.1. Link Identifier Field...............................11
4.3.2. Wavelength Restriction Field........................12
4.4. Signal processing capability restrictions................14
4.4.1. Signal Processing Exclusion XRO Subobject...........15
4.4.2. IRO subobject: signal processing inclusion..........16
5. Encoding of a RWA Path Reply..................................16
5.1. Error Indicator..........................................18
5.2. NO-PATH Indicator........................................18
6. Manageability Considerations..................................19
6.1. Control of Function and Policy...........................19
6.2. Liveness Detection and Monitoring........................19
6.3. Verifying Correct Operation..............................20
6.4. Requirements on Other Protocols and Functional Components20
6.5. Impact on Network Operation..............................20
7. Security Considerations.......................................20
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8. IANA Considerations...........................................20
8.1. New PCEP Object..........................................20
8.2. New PCEP TLV: Wavelength Selection TLV...................21
8.3. New PCEP TLV: Wavelength Restriction Constraint TLV......21
8.4. New PCEP TLV: Wavelength Allocation TLV..................21
8.5. New PCEP TLV: Optical Interface Class List TLV...........22
8.6. New PCEP TLV: Client Signal TLV..........................22
8.7. New No-Path Reasons......................................22
8.8. New Error-Types and Error-Values.........................23
8.9. New Subobject for the Exclude Route Object...............23
8.10. New Subobject for the Include Route Object..............24
9. Acknowledgments...............................................24
10. References...................................................24
10.1. Normative References....................................24
10.2. Informative References..................................25
11. Contributors.................................................27
Authors' Addresses...............................................28
1. Terminology
This document uses the terminology defined in [RFC4655], and
[RFC5440].
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Introduction
[RFC5440] specifies the Path Computation Element (PCE) Communication
Protocol (PCEP) for communications between a Path Computation Client
(PCC) and a PCE, or between two PCEs. Such interactions include
path computation requests and path computation replies as well as
notifications of specific states related to the use of a PCE in the
context of Multiprotocol Label Switching (MPLS) and Generalized MPLS
(GMPLS) Traffic Engineering.
A PCC is said to be any network component that makes such a request
and may be, for instance, an Optical Switching Element within a
Wavelength Division Multiplexing (WDM) network. The PCE, itself,
can be located anywhere within the network, and may be within an
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optical switching element, a Network Management System (NMS) or
Operational Support System (OSS), or may be an independent network
server.
This document provides the PCEP extensions for the support of
Routing and Wavelength Assignment (RWA) in Wavelength Switched
Optical Networks (WSON) based on the requirements specified in
[RFC6163] and [RFC7449].
WSON refers to WDM based optical networks in which switching is
performed selectively based on the wavelength of an optical signal.
The devices used in WSONs that are able to switch signals based on
signal wavelength are known as Lambda Switch Capable (LSC). WSONs
can be transparent or translucent. A transparent optical network is
made up of optical devices that can switch but not convert from one
wavelength to another, all within the optical domain. On the other
hand, translucent networks include 3R regenerators (Re-
amplification, Re-shaping, Re-timing) that are sparsely placed. The
main function of the 3R regenerators is to convert one optical
wavelength to another.
A Lambda Switch Capable (LSC) Label Switched Path (LSP) may span one
or several transparent segments, which are delimited by 3R
regenerators typically with electronic regenerator and optional
wavelength conversion. Each transparent segment or path in WSON is
referred to as an optical path. An optical path may span multiple
fiber links and the path should be assigned the same wavelength for
each link. In such case, the optical path is said to satisfy the
wavelength-continuity constraint. Figure 1 illustrates the
relationship between a LSC LSP and transparent segments (optical
paths).
+---+ +-----+ +-----+ +-----+ +-----+
| |I1 | | | | | | I2| |
| |o------| |-------[(3R) ]------| |--------o| |
| | | | | | | | | |
+---+ +-----+ +-----+ +-----+ +-----+
(X LSC) (LSC LSC) (LSC LSC) (LSC X)
Transparent Segment Transparent Segment
LSC LSP
Figure 1 Illustration of a LSC LSP and transparent segments
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Note that two optical paths within a WSON LSP do not need to operate
on the same wavelength (due to the wavelength conversion
capabilities). Two optical paths that share a common fiber link
cannot be assigned the same wavelength; Otherwise, the two signals
would interfere with each other. Note that advanced additional
multiplexing techniques such as polarization based multiplexing are
not addressed in this document since the physical layer aspects are
not currently standardized. Therefore, assigning the proper
wavelength on a path is an essential requirement in the optical path
computation process.
When a switching node has the ability to perform wavelength
conversion, the wavelength-continuity constraint can be relaxed, and
a LSC Label Switched Path (LSP) may use different wavelengths on
different links along its route from origin to destination. It is,
however, to be noted that wavelength converters may be limited due
to their relatively high cost, while the number of WDM channels that
can be supported in a fiber is also limited. As a WSON can be
composed of network nodes that cannot perform wavelength conversion,
nodes with limited wavelength conversion, and nodes with full
wavelength conversion abilities, wavelength assignment is an
additional routing constraint to be considered in all optical path
computation.
For example (see Figure 1), within a translucent WSON, a LSC LSP may
be established between interfaces I1 and I2, spanning 2 transparent
segments (optical paths) where the wavelength continuity constraint
applies (i.e. the same unique wavelength must be assigned to the LSP
at each TE link of the segment). If the LSC LSP induced a Forwarding
Adjacency / TE link, the switching capabilities of the TE link would
be (X X) where X refers to the switching capability of I1 and I2.
For example, X can be Packet Switch Capable (PSC), Time Division
Multiplexing (TDM), etc.
This document aligns with GMPLS extensions for PCEP [PCEP-GMPLS] for
generic properties such as label, label-set and label assignment
noting that wavelength is a type of label. Wavelength restrictions
and constraints are also formulated in terms of labels per
[RFC7579].
The optical modulation properties, which are also referred to as
signal compatibility, are already considered in signaling in
[RFC7581] and [RFC7688]. In order to improve the signal quality and
limit some optical effects several advanced modulation processing
capabilities are used. These modulation capabilities contribute not
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only to optical signal quality checks but also constrain the
selection of sender and receiver, as they should have matching
signal processing capabilities. This document includes signal
compatibility constraints as part of RWA path computation. That is,
the signal processing capabilities (e.g., modulation and Forward
Error Correction (FEC)) indicated by means of optical interface
class (OIC) must be compatible between the sender and the receiver
of the optical path across all optical elements.
This document, however, does not address optical impairments as part
of RWA path computation. See [RFC6566] for the framework for optical
impairments.
4. Encoding of a RWA Path Request
Figure 2 shows one typical PCE based implementation, which is
referred to as the Combined Process (R&WA). With this architecture,
the two processes of routing and wavelength assignment are accessed
via a single PCE. This architecture is the base architecture
specified in [RFC6163] and the PCEP extensions that are specified in
this document are based on this architecture.
+----------------------------+
+-----+ | +-------+ +--+ |
| | | |Routing| |WA| |
| PCC || +-------+ +--+ |
| | | |
+-----+ | PCE |
+----------------------------+
Figure 2 Combined Process (R&WA) architecture
4.1. Wavelength Assignment (WA) Object
Wavelength allocation can be performed by the PCE by different
means:
(a) By means of Explicit Label Control [RFC3471] where the PCE
allocates which label to use for each interface/node along the path.
The allocated labels MAY appear after an interface route subobject.
(b) By means of a Label Set where the PCE provides a range of
potential labels to allocate by each node along the path.
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Option (b) allows distributed label allocation (performed during
signaling) to complete wavelength assignment.
Additionally, given a range of potential labels to allocate, the
request SHOULD convey the heuristic / mechanism used for the
allocation.
The format of a PCReq message per [RFC5440] after incorporating the
Wavelength Assignment (WA) object is as follows:
::=
[]
Where:
::=[]
::=
[other optional objects...]
If the WA object is present in the request, it MUST be encoded after
the END-POINTS object as defined in [PCEP-GMPLS]. The WA Object is
mandatory in this document. Orderings for the other optional objects
are irrelevant.
The format of the WA object body is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Wavelength Selection TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Wavelength Restriction Constraint TLV |
. .
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. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3 WA Object
o Reserved (16 bits): Reserved for future use and SHOULD be zeroed
and ignored on receipt.
o Flags (16 bits)
One flag bit is allocated as follows:
. M (Mode - 1 bit): M bit is used to indicate the mode of
wavelength assignment. When M bit is set to 1, this indicates
that the label assigned by the PCE must be explicit. That is,
the selected way to convey the allocated wavelength is by means
of Explicit Label Control for each hop of a computed LSP.
Otherwise (M bit is set to 0), the label assigned by the PCE
need not be explicit (i.e., it can be suggested in the form of
label set objects in the corresponding response, to allow
distributed WA. If M is 0, the PCE MUST return a Label Set
Field as described in Section 2.6 of [RFC7579] in the response.
See Section 5 of this document for the encoding discussion of a
Label Set Field in a PCRep message.
All unused flags SHOULD be zeroed.
. Wavelength Selection TLV (32 bits): See Section 4.2 for
details.
. Wavelength Restriction Constraint TLV (Variable): See Section
4.3 for details.
4.2. Wavelength Selection TLV
The Wavelength Selection TLV is used to indicate the wavelength
selection constraint in regard to the order of wavelength assignment
to be returned by the PCE. This TLV is only applied when M bit is
set in the WA Object specified in Section 4.1. This TLV MUST NOT be
used when the M bit is cleared.
The encoding of this TLV is specified as the Wavelength Selection
Sub-TLV in Section 4.2.2 of [RFC7689].
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4.3. Wavelength Restriction Constraint TLV
For any request that contains a wavelength assignment, the requester
(PCC) MUST specify a restriction on the wavelengths to be used. This
restriction is to be interpreted by the PCE as a constraint on the
tuning ability of the origination laser transmitter or on any other
maintenance related constraints. Note that if the LSP LSC spans
different segments, the PCE must have mechanisms to know the
tunability restrictions of the involved wavelength converters /
regenerators, e.g. by means of the Traffic Engineering Database
(TED) either via IGP or Network Management System (NMS). Even if the
PCE knows the tunability of the transmitter, the PCC must be able to
apply additional constraints to the request.
The format of the Wavelength Restriction Constraint TLV is as
follows:
::=
()...
Where
::= []
See Section 4.3.1. for the encoding of the Link Identifiers Field.
and fields together MAY
appear more than once to be able to specify multiple restrictions.
The Wavelength Restriction Constraint TLV type is TBD3 (See Section
8.3).
The TLV data is defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action | Count | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Link Identifiers |
| . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Wavelength Restriction Field |
// . . . . //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4 Wavelength Restriction Constraint TLV Encoding
o Action (8 bits):
. 0 - Inclusive List indicates that one or more link identifiers
are included in the Link Set. Each identifies a separate link
that is part of the set.
. 1 - Inclusive Range indicates that the Link Set defines a
range of links. It contains two link identifiers. The first
identifier indicates the start of the range (inclusive). The
second identifier indicates the end of the range (inclusive).
All links with numeric values between the bounds are
considered to be part of the set. A value of zero in either
position indicates that there is no bound on the corresponding
portion of the range.
. 2-255 - For future use
Note that "links" are assumed to be bidirectional.
o Count (8 bits): The number of the link identifiers
Note that a PCC MAY add a Wavelength restriction that applies to all
links by setting the Count field to zero and specifying just a set
of wavelengths.
Note that all link identifiers in the same list must be of the same
type.
o Reserved (16 bits): Reserved for future use and SHOULD be zeroed
and ignored on receipt.
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o Link Identifiers: Identifies each link ID for which restriction
is applied. The length is dependent on the link format and the Count
field. See Section 4.3.1. for Link Identifier encoding and Section
4.3.2. for the Wavelength Restriction Field encoding, respectively.
Various encoding errors are possible with this TLV (e.g., not
exactly two link identifiers with the range case, unknown identifier
types, no matching link for a given identifier, etc.). To indicate
errors associated with this type, a new Error-Type (TBD8) and an
Error-value (Error-value=3) are assigned so that the PCE MUST send a
PCErr message with a PCEP-ERROR Object. See Section 5.1 for the
details.
4.3.1. Link Identifier Field
The link identifier field can be an IPv4 [RFC3630], IPv6 [RFC5329]
or unnumbered interface ID [RFC4203].
::=
| |
The encoding of each case is as follows:
IPv4 prefix sub-TLV
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 1 | Reserved (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 address (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 prefix Sub-TLV
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 2 | Reserved (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| IPv6 address (16 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 address (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Unnumbered Interface ID Sub-TLV
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 3 | Reserved (16 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TE Node ID (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Interface ID (32 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type (8 bits): It indicates the type of the link identifier.
Reserved (16 bits): Reserved for future use and SHOULD be zeroed
and ignored on receipt.
The Type field is extensible. Please refer to the IANA registry
allocated for Link Management Protocol (LMP) [RFC4204]:
https://www.iana.org/assignments/lmp-parameters/lmp-
parameters.xhtml#lmp-parameters-15.
4.3.2. Wavelength Restriction Field
The Wavelength Restriction Field of the Wavelength Restriction
Constraint TLV is encoded as a Label Set field as specified in
Section 2.6 in [RFC7579] with base label encoded as a 32 bit LSC
label, defined in [RFC6205]. The Label Set format is repeated here
for convenience, with the base label internal structure included.
See [RFC6205] for a description of Grid, C.S, Identifier and n, as
well as [RFC7579] for the details of each action.
0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action| Num Labels | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Grid | C.S | Identifier | n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Additional fields as necessary per action |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Action (4 bits):
0 - Inclusive List
1 - Exclusive List
2 - Inclusive Range
3 - Exclusive Range
4 - Bitmap Set
Num Labels (12 bits): It is generally the number of labels. It has a
specific meaning depending on the action value.
Length (16 bits): It is the length in bytes of the entire Wavelength
Restriction field.
The Identifier has a specific PCEP context. To clarify the
interpretation of the Identifier, the following additional
explanation is added.
Identifier (9 bits): The value to be included in the "Identifier"
field of the WDM label in RSVP-TE signaling, as defined in section
3.2 of [RFC6205]. The PCC MAY use the assigned value for the
Identifier field in the corresponding LSP-related messages in RSVP-
TE signaling.
See Sections 2.6.1 - 2.6.3 of [RFC7579] for details on additional
field discussion for each action.
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4.4. Signal processing capability restrictions
Path computation for WSON includes checking of signal processing
capabilities at each interface against requested capability; the PCE
MUST have mechanisms to know the signal processing capabilities at
each interface, e.g. by means of the Traffic Engineering Database
(TED) either via IGP or Network Management System (NMS). Moreover,
a PCC should be able to indicate additional restrictions to signal
processing compatibility, either on the endpoint or any given link.
The supported signal processing capabilities considered in the RWA
Information Model [RFC7446] are:
. Optical Interface Class List
. Bit Rate
. Client Signal
The Bit Rate restriction is already expressed in [PCEP-GMPLS] in the
BANDWIDTH object.
In order to support the Optical Interface Class information and the
Client Signal information new TLVs are introduced as endpoint-
restriction in the END-POINTS type Generalized endpoint:
. Client Signal TLV
. Optical Interface Class List TLV
The END-POINTS type generalized endpoint is extended as follows:
::=
[...]
Where
signal-compatibility-restriction ::=
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The encoding for the Optical Interface Class List (TBD5) is
described in Section 4.1 of [RFC7581].
The encoding for the Client Signal Information (TBD6) is described
in Section 4.2 of [RFC7581].
4.4.1. Signal Processing Exclusion XRO Subobject
The PCC/PCE should be able to exclude particular types of signal
processing along the path in order to handle client restriction or
multi-domain path computation. [RFC5440] defines how Exclude Route
Object (XRO) subobject is used. In this draft, we add a new XRO
subobject, signal processing subobject.
In order to support the exclusion a new XRO subobject is defined:
the signal processing exclusion:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type =TBD | Length | Reserved | Attribute |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-sub objects |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5 Signaling Processing XRO Subobject
Refer to [RFC5521] for the definition of X, Length and Attribute.
Type (7 bits): The Type of the XRO sub-sub objects. See below for
the two TBD values (TBD9 and TBD10) to be assigned by the IANA.
Reserved bits (8 bits) are for future use and SHOULD be zeroed and
ignored on receipt.
The Attribute field (8 bits): [RFC5521] defines several Attribute
values; the only permitted Attribute values for this subobject are
0 (Interface) or 1 (Node).
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The permitted sub-sub objects are the Optical Interface Class List
and the Client Signal information whose encodings are described in
Section 4.1 and Section 4.2 of [RFC7581], respectively.
The XRO needs to support the new subobject types:
Type Sub-subobject
TBD9 Optical Interface Class List
TBD10 Client Signal Information
4.4.2. IRO subobject: signal processing inclusion
Similar to the XRO subobject, the PCC/PCE should be able to include
particular types of signal processing along the path in order to
handle client restriction or multi-domain path computation.
[RFC5440] defines how Include Route Object (IRO) subobject is used.
In this draft, we add a new IRO subobject, signal processing
subobject.
The IRO needs to support the new subobject types as defined in
Section 4.2 [RFC7689] "WSON Processing Hop Attribute TLV" (TBD9)
defined for ERO in Section 4.2 [RFC7689] to the PCEP IRO object
[RFC5440]:
Type Sub-subobject
TBD11 Optical Interface Class List
TBD12 Client Signal Information
5. Encoding of a RWA Path Reply
This section provides the encoding of a RWA Path Reply for
wavelength allocation request as discussed in Section 4. Recall that
wavelength allocation can be performed by the PCE by different
means:
(a) By means of Explicit Label Control (ELC) where the PCE
allocates which label to use for each interface/node along the
path.
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(b) By means of a Label Set where the PCE provides a range of
potential labels to allocate by each node along the path.
Option (b) allows distributed label allocation (performed during
signaling) to complete wavelength allocation.
The Wavelength Allocation TLV type is TBD4 (See Section 8.4). Note
that this TLV is used for both (a) and (b). The TLV data is defined
as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Identifier |
| . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Allocated Wavelength(s) |
// . . . . //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6 Wavelength Allocation TLV Encoding
o Reserved (15 bits): Reserved for future use.
o M (Mode): 1 bit
- 0 indicates the allocation is under Explicit Label Control.
- 1 indicates the allocation is expressed in Label Sets.
Note that all link identifiers in the same list must be of the same
type.
o Link Identifier: Identifies the interface to which assignment
wavelength(s) is applied. See Section 4.3.1. for Link Identifier
encoding.
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o Allocated Wavelength(s): Indicates the allocated wavelength(s) to
be associated with the Link Identifier. See Section 4.3.2 for
encoding details.
This TLV is encoded as an attributes TLV, per [RFC5420], which is
carried in the Hop Attribute Subobjects per [RFC7570].
5.1. Error Indicator
To indicate errors associated with the RWA request, a new Error Type
(TBD8) and subsequent error-values are defined as follows for
inclusion in the PCEP-ERROR Object:
A new Error-Type (TBD8) and subsequent error-values are defined as
follows:
. Error-Type=TBD8; Error-value=1: if a PCE receives a RWA
request and the PCE is not capable of processing the request
due to insufficient memory, the PCE MUST send a PCErr message
with a PCEP-ERROR Object (Error-Type=TBD8) and an Error-
value(Error-value=1). The PCE stops processing the request.
The corresponding RWA request MUST be cancelled at the PCC.
. Error-Type=TBD8; Error-value=2: if a PCE receives a RWA
request and the PCE is not capable of RWA computation, the PCE
MUST send a PCErr message with a PCEP-ERROR Object (Error-
Type=TBD8) and an Error-value (Error-value=2). The PCE stops
processing the request. The corresponding RWA computation
MUST be cancelled at the PCC.
. Error-Type=TBD8; Error-value=3: if a PCE receives a RWA
request and there are syntactical encoding errors (e.g., not
exactly two link identifiers with the range case, unknown
identifier types, no matching link for a given identifier,
etc.), the PCE MUST send a PCErr message with a PCEP-ERROR
Object (Error-Type=TBD8) and an Error-value (Error-value=3).
5.2. NO-PATH Indicator
To communicate the reason(s) for not being able to find RWA for the
path request, the NO-PATH object can be used in the corresponding
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response. The format of the NO-PATH object body is defined in
[RFC5440]. The object may contain a NO-PATH-VECTOR TLV to provide
additional information about why a path computation has failed.
One new bit flag is defined to be carried in the Flags field in the
NO-PATH-VECTOR TLV carried in the NO-PATH Object.
. Bit TBD7: When set, the PCE indicates no feasible route was
found that meets all the constraints (e.g., wavelength
restriction, signal compatibility, etc.) associated with RWA.
6. Manageability Considerations
Manageability of WSON Routing and Wavelength Assignment (RWA) with
PCE must address the following considerations:
6.1. Control of Function and Policy
In addition to the parameters already listed in Section 8.1 of
[RFC5440], a PCEP implementation SHOULD allow configuration of the
following PCEP session parameters on a PCC:
. The ability to send a WSON RWA request.
In addition to the parameters already listed in Section 8.1 of
[RFC5440], a PCEP implementation SHOULD allow configuration of the
following PCEP session parameters on a PCE:
. The support for WSON RWA.
. A set of WSON RWA specific policies (authorized sender,
request rate limiter, etc).
These parameters may be configured as default parameters for any
PCEP session the PCEP speaker participates in, or may apply to a
specific session with a given PCEP peer or a specific group of
sessions with a specific group of PCEP peers.
6.2. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in section 8.3 of [RFC5440].
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6.3. Verifying Correct Operation
Mechanisms defined in this document do not imply any new
verification requirements in addition to those already listed in
section 8.4 of [RFC5440]
6.4. Requirements on Other Protocols and Functional Components
The PCEP Link-State mechanism [PCEP-LS] may be used to advertise
WSON RWA path computation capabilities to PCCs.
6.5. Impact on Network Operation
Mechanisms defined in this document do not imply any new network
operation requirements in addition to those already listed in
section 8.6 of [RFC5440].
7. Security Considerations
The security considerations discussed in [RFC5440] are relevant for
this document, this document does not introduce any new security
issues. If an operator wishes to keep private the information
distributed by WSON, PCEPS [RFC8253] SHOULD be used.
8. IANA Considerations
IANA maintains a registry of PCEP parameters. IANA has made
allocations from the sub-registries as described in the following
sections.
8.1. New PCEP Object
As described in Section 4.1, a new PCEP Object is defined to carry
wavelength assignment related constraints. IANA is to allocate the
following from "PCEP Objects" sub-registry
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-objects):
Object Class Name Object Reference
Value Type
---------------------------------------------------------
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TBD1 WA 1: Wavelength-Assignment [This.I-D]
8.2. New PCEP TLV: Wavelength Selection TLV
As described in Sections 4.2, a new PCEP TLV is defined to indicate
wavelength selection constraints. IANA is to allocate this new TLV
from the "PCEP TLV Type Indicators" subregistry
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
indicators).
Value Description Reference
---------------------------------------------------------
TBD2 Wavelength Selection [This.I-D]
8.3. New PCEP TLV: Wavelength Restriction Constraint TLV
As described in Sections 4.3, a new PCEP TLV is defined to indicate
wavelength restriction constraints. IANA is to allocate this new TLV
from the "PCEP TLV Type Indicators" subregistry
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
indicators).
Value Description Reference
---------------------------------------------------------
TBD3 Wavelength Restriction [This.I-D]
Constraint
8.4. New PCEP TLV: Wavelength Allocation TLV
As described in Section 5, a new PCEP TLV is defined to indicate the
allocation of wavelength(s) by the PCE in response to a request by
the PCC. IANA is to allocate this new TLV from the "PCEP TLV Type
Indicators" subregistry
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
indicators).
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Value Description Reference
---------------------------------------------------------
TBD4 Wavelength Allocation [This.I-D]
8.5. New PCEP TLV: Optical Interface Class List TLV
As described in Section 4.4, a new PCEP TLV is defined to indicate
the optical interface class list. IANA is to allocate this new TLV
from the "PCEP TLV Type Indicators" subregistry
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
indicators).
Value Description Reference
---------------------------------------------------------
TBD5 Optical Interface [This.I-D]
Class List
8.6. New PCEP TLV: Client Signal TLV
As described in Section 4.4, a new PCEP TLV is defined to indicate
the client signal information. IANA is to allocate this new TLV from
the "PCEP TLV Type Indicators" subregistry
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-tlv-type-
indicators).
Value Description Reference
---------------------------------------------------------
TBD6 Client Signal Information [This.I-D]
8.7. New No-Path Reasons
As described in Section 5.2., a new bit flag are defined to be
carried in the Flags field in the NO-PATH-VECTOR TLV carried in the
NO-PATH Object. This flag, when set, indicates that no feasible
route was found that meets all the RWA constraints (e.g., wavelength
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restriction, signal compatibility, etc.) associated with a RWA path
computation request.
IANA is to allocate this new bit flag from the "PCEP NO-PATH-VECTOR
TLV Flag Field" subregistry
(http://www.iana.org/assignments/pcep/pcep.xhtml#no-path-vector-
tlv).
Bit Description Reference
-----------------------------------------------------
TBD7 No RWA constraints met [This.I-D]
8.8. New Error-Types and Error-Values
As described in Section 5.1, new PCEP error codes are defined for
WSON RWA errors. IANA is to allocate from the ""PCEP-ERROR Object
Error Types and Values" sub-registry
(http://www.iana.org/assignments/pcep/pcep.xhtml#pcep-error-object).
Error- Meaning Error-Value Reference
Type
---------------------------------------------------------------
TBD8 WSON RWA Error 1: Insufficient [This.I-D]
Memory
2: RWA computation [This.I-D]
Not supported
3: Syntactical [This.I-D]
Encoding error
8.9. New Subobject for the Exclude Route Object
The "PCEP Parameters" registry contains a subregistry "PCEP Objects"
with an entry for the Exclude Route Object (XRO). IANA is requested
to add a further subobject that can be carried in the XRO as
follows:
Subobject Type Reference
----------------------------------------------------------
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TBD9 Optical Interface Class List [This.I-D]
TBD10 Client Signal Information [This.I-D]
8.10. New Subobject for the Include Route Object
The "PCEP Parameters" registry contains a subregistry "PCEP Objects"
with an entry for the Include Route Object (IRO). IANA is requested
to add a further subobject that can be carried in the IRO as
follows:
Subobject Type Reference
----------------------------------------------------------
TBD11 Optical Interface Class List [This.I-D]
TBD12 Client Signal Information [This.I-D]
9. Acknowledgments
The authors would like to thank Adrian Farrel and Julien Meuric for
many helpful comments that greatly improved the contents of this
draft.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3630] D. Katz, K. Kompella, D. Yeung, "Traffic Engineering (TE)
Extensions to OSPF Version 2", RFC 3630, September 2003.
[RFC5329] A. Lindem, Ed., "Traffic Engineering Extensions to OSPF
Version 3", RFC 5329, September 2008.
[RFC5440] JP. Vasseur, Ed., JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
March 2009.
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[RFC6205] Tomohiro, O. and D. Li, "Generalized Labels for Lambda-
Switching Capable Label Switching Routers", RFC 6205,
January, 2011.
[RFC7570] C. Margaria, et al., "Label Switched Path (LSP) Attribute
in the Explicit Route Object (ERO)", RFC 7570, July 2015.
[RFC7579] G. Bernstein and Y. Lee, "General Network Element
Constraint Encoding for GMPLS Controlled Networks", RFC
7579, June 2015.
[RFC7581] G. Bernstein and Y. Lee, "Routing and Wavelength
Assignment Information Encoding for Wavelength Switched
Optical Networks", RFC7581, June 2015.
[RFC7689] Bernstein et al., "Signaling Extensions for Wavelength
Switched Optical Networks", RFC 7689, November 2015.
[RFC7688] Y. Lee, and G. Bernstein, "OSPF Enhancement for Signal and
Network Element Compatibility for Wavelength Switched
Optical Networks", RFC 7688, November 2015.
[RFC8174] B. Leiba, "Ambiguity of Uppercase vs Lowercase in RFC 2119
Key Words", RFC 8174, May 2017.
[RFC8253] D. Lopez, O. Gonzalez de Dios, Q. Wu, D. Dhody, "PCEPS:
Usage of TLS to Provide a Secure Transport for the Path
Computation Element Communication Protocol (PCEP)", RFC
8253, October 2017.
[PCEP-GMPLS] C. Margaria, et al., "PCEP extensions for GMPLS",
draft-ietf-pce-gmpls-pcep-extensions, work in progress.
10.2. Informative References
[RFC3471] Berger, L. (Editor), "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description", RFC
3471. January 2003.
[RFC4203] K. Kompella, Ed., Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, October 2005.
[RFC4204] J. Lang, Ed., "Link Management Protocol (LMP)", RFC 4204,
October 2005.
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[RFC4655] A. Farrel, JP. Vasseur, G. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC5420] Farrel, A. "Encoding of Attributes for MPLS LSP
Establishment Using Resource Reservation Protocol Traffic
Engineering (RSVP-TE)", RFC5420, February 2009.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) communication Protocol", RFC 5440, March
2009.[RFC5521] Oki, E, T. Takeda, and A. Farrel,
"Extensions to the Path Computation Element Communication
Protocol (PCEP) for Route Exclusions", RFC 5521, April
2009.
[RFC6163] Lee, Y. and Bernstein, G. (Editors), and W. Imajuku,
"Framework for GMPLS and PCE Control of Wavelength
Switched Optical Networks", RFC 6163, March 2011.
[RFC6566] Lee, Y. and Berstein, G. (Editors), "A Framework for the
Control of Wavelength Switched Optical Networks (WSONs)
with Impairments", RFC 6566, March 2012.
[RFC7446] Y. Lee, G. Bernstein, (Editors), "Routing and Wavelength
Assignment Information Model for Wavelength Switched
Optical Networks", RFC 7446, February 2015.
[RFC7449] Y. Lee, G. Bernstein, (Editors), "Path Computation Element
Communication Protocol (PCEP) Requirements for Wavelength
Switched Optical Network (WSON) Routing and Wavelength
Assignment", RFC 7449, February 2015.
[PCEP-LS] Y. Lee, et al., "PCEP Extension for Distribution of Link-
State and TE information for Optical Networks", draft-lee-
pce-pcep-ls-optical, work in progress.
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11. Contributors
Fatai Zhang
Huawei Technologies
Email: zhangfatai@huawei.com
Cyril Margaria
Nokia Siemens Networks
St Martin Strasse 76
Munich, 81541
Germany
Phone: +49 89 5159 16934
Email: cyril.margaria@nsn.com
Oscar Gonzalez de Dios
Telefonica Investigacion y Desarrollo
C/ Emilio Vargas 6
Madrid, 28043
Spain
Phone: +34 91 3374013
Email: ogondio@tid.es
Greg Bernstein
Grotto Networking
Fremont, CA, USA
Phone: (510) 573-2237
Email: gregb@grotto-networking.com
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Authors' Addresses
Young Lee, Editor
Huawei Technologies
1700 Alma Drive, Suite 100
Plano, TX 75075, USA
Phone: (972) 509-5599 (x2240)
Email: leeyoung@huawei.com
Ramon Casellas, Editor
CTTC PMT Ed B4 Av. Carl Friedrich Gauss 7
08860 Castelldefels (Barcelona)
Spain
Phone: (34) 936452916
Email: ramon.casellas@cttc.es
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